Thinking in Assemblies

Thinking in Assemblies

Using Wall Sections to Make Better Material Choices

Thinking in Assemblies

Using Wall Sections to Make Better Material Choices authors

Contributors

April 2016

Christopher Lee, LEED AP BD+C Re:Vision Architecture

Christopher Boccella CVMNEXT Construction

for more information contact: info@revisionarch.com

Nicole Campion, PhD, LEED GA

Garrett McKissock SIGA Ethan Lee Swarthmore College

Abstract Assemblies, like the wall section, are fundamental to how we think about and construct our buildings. They have a significant impact on a project’s operating energy and embodied carbon footprint (ECF).

Traditionally, material selection has been driven by performance, cost, and aesthetics; however, the emerging focus on environmental and health transparency tools is beginning to transform the industry.

Designers, contractors and developers are beginning to consider new priorities like lifecycle assessment, toxicity, and moisture transport as they select materials.

While minimizing operating energy is still the primary design strategy for high performance buildings, minimizing embodied carbon is also becoming important to clients and designers. This study puts particular emphasis on embodied carbon footprint modeling to better understand its role in the decision making process for materials.

The research had two parts:

Part One To better understand how to take a more holistic approach to product selection, this study evaluates and compares 12’H x 24’W wall sections of varying construction materials. Each assembly was evaluated using a multi-attribute analysis that included the following metrics:

Embodied Carbon Footprint (ECF) Materials Toxicity Moisture Transportation Thermal Resistance End of life Impact Cost

• Develop a holistic methodology for multi-attribute assessment of a wall assembly and its individual components given evolving priorities towards the environment and health.

• Assess how built wall sections perform against the new criteria and how they could be improved to lower embodied carbon, adhere to Red List compliant chemicals, and/or reduce their contribution to land fill waste at the end of their useful life.

Part Two • Create wall sections of similar thermal resistance and construction type, to evaluate insulation within the new sets of environmental and health criteria.

Contents INTRODUCTION­............................................................................................................................. 2 METHODOLOGY............................................................................................................................. 4 STUDY OF FIVE SECTIONS............................................................................................................. 8

DESIGN DECISION ............................................................................................................. 8

Embodied Carbon Footprint...................................................................................... 10

Material Toxicity and Transparency............................................................................ 16

Moisture Performance............................................................................................... 20

Thermal Performance................................................................................................ 22

Material Cost.............................................................................................................. 23

End-of-Life.................................................................................................................. 24

DESIGN DECISION ANALYSIS............................................................................................ 26

Design Decision of Five Wall Sections....................................................................... 26

STUDY OF FIVE SECTIONS CONCLUSION........................................................................ 30

NORMALIZED SECTION STUDY................................................................................................... 34

NORMALIZED SECTION STUDY ANALYSIS....................................................................... 34

Embodied Carbon Footprint...................................................................................... 36

Material Toxicity and Transparency............................................................................ 40

Thermal Performance................................................................................................ 42

Material Cost............................................................................................................. 43

End-of-Life................................................................................................................. 44

DESIGN DECISION ANALYSIS........................................................................................... 46

Design Decision of Normalized Wall Study............................................................... 46

NORMALIZED SECTION STUDY CONCLUSIONS............................................................. 50

Collaborators................................................................................................................................ 51 References................................................................................................................................... 51

page 2

INTRODUCTION The idea for “Thinking in Assemblies” began as most ideas do, with a conversation about potential and possibility. Within Re:Vision Architecture, we were meeting with a number of manufacturer’s sustainability managers and product managers. We talked with these sustainability professionals about third party reporting methods and certifications such as Health Product Declaration, Environmental Product Declaration, MSDS, the Declare Label, Cradle to Cradle, and the overall importance of ingredients and environmental transparency in the building industry. Through these conversations, we learned of uncertainty about knowing which third party certification would become important in the marketplace, which ones were worth putting resources behind, and hesitation to participate in third party reporting due to the required disclosure of proprietary ingredients.

We also shared some barriers to conducting materials transparency research as required for Living Building Challenge (LBC) projects: the time, finding the right resources, and finding and talking to the right person within companies to get information needed to complete LBC documentation. We all wanted a single resource, a single tool, or a single certification that would aggregate all of a product’s attributes and environmental impacts in one place.

We knew the “Living Product Challenge” by the International Living Future Institute was due for release which would begin to collect this data. However, we didn’t know how quickly it would be adopted by the building industry so we decided to see if aggregating multiple tools available today

could get us closer to this goal. The research of “Thinking in Assemblies” is a proposal for a methodology for the holistic and transparent analysis of materials. We aim to take off the single attribute blinders traditionally used to evaluate materials and provide a wide look at the impacts our material selection has across multiple metrics, such as cost and performance, as well as toxicity, embodied carbon, moisture transport, and end of life.

Why Assemblies?

The “Thinking in Assemblies” methodology we are proposing is about a different approach to product selection and research. Rarely is anything in the built environment made of a single ingredient or product, so why do we approach materials research and selection at the product level? We should research like we build and think in terms of building assemblies. By zooming out to this larger scale, we believe the proposed methodology can be more valuable in the process of material selection for buildings. Wall assemblies are high impact in terms of cost, performance and the sheer amount of materials used. For this reason, wall assemblies are an ideal place to begin to reduce environmental and health impacts.

page 3

Why should you care?

There are many reasons but, for us, it comes down to three key issues.

responsibility As designers, contractors, engineers, and developers, we help select the products and materials used in our buildings. Ingredients on the Red List represent some of the worst-in-class and carcinogenic chemicals that are currently prolific in the built environment because we put them in our buildings. Just as architects are responsible to provide accessibility, egress, and energy performance, we should also be mindful of selecting of materials that minimize harm to our clients and the environment throughout their lifecycle.

influence

right to know

With product selection for projects comes buying power. Buying power is one of the most influential tools we have in a market economy to help move and change the building product industry. If product specifiers favored Red List Free rigid roofing insulations, manufactures making Red List free products would see great growth, while competitor products with Red List ingredients would be faced with the decision to lose market share or adapt to the demands of the industry to remain competitive.

Nutrition labels let us know what we put into our bodies, why shouldn’t we know what is in the building products we live with each day at work, school, and home? Right now we have the ability to look at a food label and make an informed decision for our health. Most people cannot evaluate MSDS or HPD to make more informed decisions on the impact a material could have on their health. Disclosing ingredients or product life cycle impacts is good for consumers and also for manufactures so they can better understand impacts beyond their factory doors.

page 4

METHODOLOGY Each 12’H x 24’W wall section was evaluated using the below criteria as a guide for assessment.

EMBODIED CARBON FOOTPRINT (ECF) a. Embodied carbon footprint (ECF) via Athena Impact Estimator for Buildings b. Available specific and industry-wide EPDs when input was unavailable in Athena MATERIALS TOXICITY & TRANSPARENCY a. Living Building Challenge’s v3 Red List b. Available specific and industry-wide EPDs PERFORMANCE a. Moisture Transport in wall assembly assessed using USai modeling software by SIGA b. Thermal resistance per manufacturer provided information

END OF LIFE (EOL) a. End of life for the product determine by best practice and contacting manufacturers COST a. Materials cost provided by a construction cost estimator CVMnext Construction

page 5

DESIGN DECISION MATRIX A Design Decision Matrix was developed to incorporate the five metrics into a tool to score each assembly. The method for the Design Decision Matrix is as follows: - 10-points were assigned to each of the five metrics for a maximum total of 50 points per assembly. The assembly’s predicted Moisture Performance was evaluated with a pass/fail.

Criteria Points

Cost

Embodied Toxicity R-Value Carbon

End of Life

1

High

High

High

Low

Landfill

Low

Low

Low

High

Recycle

2 3

- The criteria points were determined by assessing the maximum and minimum of each of the metrics as shown in Figure 1.

4

- The following descriptions and figures assume an equal weighting across all five metrics. However, the Design Decision Matrix was developed such that the weighting of each metric could be adjusted to represent the needs and goals of the project. For example, you could weigh the matrix such that cost, toxicity, and performance were twice as important as end of life and embodied carbon.

6

5

7 8 9 10

Figure 1: Design Decision Matrix Diagram

STUDY OF FIVE SECTIONS

page 8

STUDY OF FIVE SECTIONS

interior

exterior

The following pages outline the analysis and findings of our research. The assemblies selected have been used on built projects and include all of the various insulation types.

Assembly Inventory Five unique 12’H x 24’W wall assemblies were analyzed as shown below in Table 1.

METAL STUD

WOOD STUD

CMU

Cedar Wood Tongue and Groove Siding

Exterior Paint

Stone Veneer

WD Furring Strips

Cement Fiber Board Panel

Mineral Wool Insulation

Polyiso Insulation

Metal Z Girts

Air and Vapor Barrier

Air and Vapor Barrier

Mineral Wool Insulation

CMU Block

Plywood Sheathing Spray Foam Metal Stud GWB Interior Paint

Interior Paint

DOUBLE WOOD STUD Cement Fiber Board Panel WD Furring Strips

TJI Cement Fiber Board WD Furring Strops Air and Vapor Barrier

FG Mat Gypsum Sheathing

Plywood Sheathing

Plywood Sheathing

Full Cavity DensityPack Cellulose

Air and Vapor Barrier

Air and Vapor Barrier

Plywood Sheathing

Fiberglass Insulation

Fiberglass Insulation

Wood Studs

Oriented Strand Board

Wood Stud

GWB

Deep TJI

GWB

Interior Paint

GWB

Interior Paint

Table 1: Wall Assembly Breakdown from Wall Exterior to Interior

Plywood Sheathing

Interior Paint

page 9

METAL STUD

WOOD STUD

CMU

DOUBLE WOOD STUD

TJI

page 10

STUDY OF FIVE SECTIONS Embodied Carbon footprint Athena Impact Estimator for Building User Guide Notes & Inputs

“

LCA is a predictive science with uncertainties and data gaps. It should be used as an estimating tool, not a tool that measures precisely. This means it should inform but not necessarily dictate design decisions. Most importantly, LCA addresses only some of the environmental impacts of interest in a sustainability agenda. The other impacts need to be measured with other tools.

–Guide to Whole Building LCA in Green Building Programs, March 2014, pg. 27

“

”

Assumptions and uncertainties are inherent to any LCA calculation. In our opinion, some of the uncertainties have balancing effects on the results, so that the end result is still often within an acceptable margin of error. In our opinion, LCA results with the IE4B should be viewed with a 15% margin of error perspective. In other words, we consider a comparative impact measure difference of 15% or less between two design scenarios as being equal or insignificant.

–User Guide September 2014, pg. 15

”

Model Inputs: - 50 year time span - Average USA data - Cradle to gate analysis - Life cycle input related to components (see Table 2)

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INSULATION

Wall Assembly

Wall Material

Athena Input

Cedar Wood Tongue and Groove Siding

Cedar Wood Tongue and Groove Siding

Cement Fiber Board Panel

Fiber Cement

Stone Veneer

Natural Stone

WD Furring Strips

Small Dimension Softwood Lumber, Kiln-Dried

Air and Vapor Barrier

Air Barrier

Fiberglass Mat Gypsum Sheathing

1/2” Gypsum Fiber Gypsum Board

Plywood Sheathing

Softwood Plywood

Oriented Strand Board

Oriented Strand Board

Metal Z Girts

Bolts Fasteners Clips

Steel/Metal Stud

Galvanized Studs

Wood Stud

Small Dimension Softwood Lumber, kiln-Dried

CMU Block

8” Concrete Block

Deep TJI

Parallel Strand Lumber

GWB

5/8” Regular Gypsum Board

Interior Paint

Solvent Based Alkyd paint

Polyiso Insulation

Polyiso Foam Board

Fiberglass

FG Batt R 11-15

Mineral wool

MW Batt R 11-15

Spray Foam

Hand calculation

Cellulose

Blown Cellulose

Table 2: Athena Life Cycle Unit Processes

page 12

STUDY OF FIVE SECTIONS Embodied Carbon footprint Life Cycle Impact Assessment Results The embodied carbon totals and respective weights of the materials used in each of the five wall assemblies can be found in Figure 2.

FINDINGS OVERVIEW - The mineral wool insulation had a higher embodied carbon footprint relative to its weight – showing that the weight of a product does not necessarily correlate to the embodied carbon footprint associated with the product.

- The stone veneer found in the CMU assembly, contributed to 44% of the total embodied carbon footprint.

- Of the insulations used, the order of total embodied carbon footprint from high to low is:

- The spray foam found in the Metal Stud assembly and the concrete blocks found in the CMU assembly were the two materials with the highest weight and embodied carbon footprint (ECF) out of all the components analyzed.

Spray foam Fiberglass

- 3 ½” - 90 kg of CO2 eq

- Spray Foam of Assembly - Weight: 57%; ECF: 80% - Concrete Block of Assembly - Weight: 74%; ECF: 45%

Polyiso

- 1”

Cellulose

- 12” - 60 kg of CO2 eq

- Gypsum board (GWB), used in four out of five wall assemblies, averaged 12% to 20% of the total assembly weight and 2% to 13% of the total embodied carbon footprint.

- When investigating spray foam we wondered why it had the highest ECF, Spray foam typically has two sides.

Side A consists of pMDI (polymeric methylene diphenyl diisocyanate) and Side B is a mixture of polyols (polyster or mannich), fire retardants (TCPP or brominated), and blowing agents (HFC). Depending on the application process, the blowing agent can have the highest contribution to ECF followed by the pMDI [1]

- Plywood sheathing, found in four out of five wall assemblies, averaged 11% to 20% of the total assembly weight and 2% to 10% of the total embodied carbon footprint.

- Cement fiber board panels, found in three out of five wall assemblies, averaged 20% to 30% of the assembly weight and 25% to 30% of the total embodied carbon.

- 5 ½” - 4,059 kg of CO2 eq

Mineral wool - 5”

- 284 kg of CO2 eq - 61 kg of CO2 eq

- Per the SPFA [1], 1m2 of 1 inch thick medium density spray foam represents 27.6 kg CO2 eq.; 288 sf=26.75m2 26.75m2 x 27.6 kg CO2 eq = 738 kg CO2 eq per in. of SF 738 kg CO2 x 5 1/2” = 4,059 kg of CO2 eq

9000

6000

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8000 5000

5000 3000 4000

3000

2000

2000 1000 1000

0

0 Weight

ECF

Metal Stud

Weight

ECF

Wood Stud

Weight

ECF

CMU

Figure 2: Weight and Embodied Carbon Footprint of Materials Found in Five Wall Assemblies.

Weight

ECF

Double Wood Stud

Weight

ECF

TJI

Embodied Carbon Footprint (kg CO2 eq.)

4000

Weight (kg)

weight (metric tons)

6000

embodied carbon (kg CO2 eq.)

7000

ECF

ECF

page 14

STUDY OF FIVE SECTIONS Embodied Carbon footprint

ECF

METAL sTUD assembly

ECF

6,158 kg CO2 eq.

ECF

Embodied Carbon Hot-Spots ECF 1. Spray Foam 2. Wood Siding 3. Metal Studs

2,632 kg 5,802 lbs

WOOD sTUD assembly

ECF

1,086 kg CO2 eq.

Embodied Carbon Hot-SpotsECF 1. Cement Fiberboard 2. Mineral Wool 3. Gypsum Wall Board

1,383 kg 3,049 lbs

CMU assembly

2,859 kg CO2 eq.

Embodied Carbon Hot-Spots 1. CMU 2. Stone Veneer 3. Mineral Wool

8,742 kg 19,273 lbs

ECF

page 15

Double Wood stud assembly ECF

TJI assembly

962 kg CO2 eq.

1,183 kg CO2 eq.

Embodied Carbon Hot-Spots 1. Cement Fiber Board 2. Fiberglass Insulation 3. FG Mat Gypsum Board

Embodied Carbon Hot-Spots 1. TJI 2. Cement Fiber Board 3. OSB

1,601 kg 3,532 lbs

2,018 kg 4,451 lbs

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STUDY OF FIVE SECTIONS MATERIAL TOXICITY + TRANSPARENCY For each product, we reviewed Environmental Product Declarations (EPDs), Health Product Declarations (HPDs), Material Safety Data Sheets (MSDS), and other published product information to evaluate toxicity and transparency.

aSSEMBLY cOMPONENT LIST

A summary of the findings is noted in Table 3. How these findings relate to the material transparency of each wall section can be found in Figure 3 (page 18).

Living Building Challenge v3 Red List

Environmental Product Declaration

Interior Paint: Sherwin Williams: Harmony

Red List Free I10-E4 (9/2012): Proprietary Ingredients

Gypsum Wall Board: USG Fiberrock Abuse Resistant Panels

Red List Free Fully Disclosed

Industry Wide

Spray Foam Insulation: Demilec: Heat Lok Soy 200 Plus

Noncompliant: Foam insulation is not allowed in cavity-fill application as many Red List Free alternatives exist

Industry Wide

Plywood: Roy O’Martin

Exception I10-E11 (1/2009): Composite Wood Sheet Goods

Industry Wide

Air and Vapor Barrier: Vaproshield: Wrap Shield

DECLARE LABEL: Red List Free; Fully Disclosed

Polyiso Insulation: DOW: Thermax CI

Exception I10-E21 (9/2010): HFRs in Foam Insulation (exterior)

Tongue and Groove Siding: Cambia By NFP: FSC Yellow Poplar

Red List Free Fully Disclosed

Exterior Paint: Benjamin Moore Natura

Red List Free I10-E4 (9/2012): Proprietary Ingredients

Wood Studs: Roy O’Martin

Red List Free Fully Disclosed

Industry Wide

page 17

aSSEMBLY cOMPONENT LIST

Living Building Challenge v3 Red List

Environmental Product Declaration

Fiberglass Insulation: Knauf EcoBatt

DECLARE LABEL: Red List Free; Fully Disclosed

Product Specific

Mineral Wool Insulation: Thermafiber Rainscreen HD

Exception I10-E9 (3/2013): Phenol Formaldehyde in Mineral Wool Note - Outside of air barrier

Product Specific

Cement Fiber Board: James Hardie

Red List Free I10-E4 (9/2012): Proprietary Ingredients

Oriented Strand Board: Roy O’Martin

Exception I10-E11 (1/2009): Composite Wood Sheet Goods

Deep TJI: Weyerhaeuser TJI Joist

Exception I10-E10 (8/2008): Structural Composite Wood Members

Cellulose Insulation: GreenFiber Cellulose

DECLARE LABEL: Red List Free; Fully Disclosed

Industry Wide

Metal Z Girts: Clark Dietrich

Red List Free Fully Disclosed

Product Specific

CMU Block: Fizzano Brothers Concrete

Red List Free Fully Disclosed

Stone Veneer: Meshoppen Stone - Bluestone

Red List Free Fully Disclosed

Mat Gypsum Sheathing: USG

Red List Free I10-E4 (9/2012): Proprietary Ingredients

Wood Furring Strips: Roy O’Martin

Red List Free Fully Disclosed

Table 3: Materiality for all Five Wall Assemblies [4]

Industry Wide

page 18

STUDY OF FIVE SECTIONS MATERIAL TOXICITY + TRANSPARENCY

METAL sTUD assembly

wOOD sTUD assembly

cmu assembly

9 PRODUCTS

11 PRODUCTS

6 PRODUCTS

33%

67% 50%

45% 55%

Figure 3: Material Transparency

50%

page 19

dOUBLE wOOD stud assembly

tji assembly

9 PRODUCTS

9 PRODUCTS

33%

67%

33%

67%

Red List or Exception No Red List

page 20

STUDY OF FIVE SECTIONS moisture performance Condensation analysis was performed by SIGA for each wall assembly using USai modeling software. The results determined if condensation would develop in an assembly and, if so, if the assembly would be able to breathe enough to allow the condensation to dry out. This assessment has become increasingly important for high performance assemblies as more insulation is added to building exteriors and smart membranes are used. In each graph, the condensation area is noted by the blue line on the grey bar which is where the Water Pressure line intersects the Saturation Pressure line.

Each assembly showed potential condensation in December and January that would dry out within one to four months depending on the assembly. In the case of the CMU assembly, condensation formed because the stone façade was not drying out during the summer months. The value of moisture analysis was seen though SIGA’s analysis which illustrated that an impermeable membrane would needed to protect the CMU rather than a permeable membrane.

Relative humidity [%] 66.8 Interface 2 - 3 gc [g/m²] 20 Ma [g/m²] 20 Ma: accumulated moisture contents Gc: rate of condensation

METAL sTUD assembly

62.1

59.3

-7 13

-52

57.8

62.9

66.3

64.4

67

69.5

68.6

65.2

65.2

-

2.947 page 21

Graphs in equivalent air thickness: January Project:

Vision Architecture_Double Stud

printed on: 9/2/2015 12:04:06 PM

page 3 of 4

Hygrothermal caracteristics First Month: January Interior Temperature [°C] Relative humidity [%] Exterior Temperature [°C] Relative humidity [%] Water [Pa] Interface 5 -presure 6

Jan.

Feb.

Mar.

Apr.

20 71.6

June

20 81.8

July

Aug.

Sept.

Oct.

Nov.

20 59.3

Dec.

20 50.1

20 52.3

20 56.1

20 63.3

20 86.2

20 86.1

20 78.4

20 66.7

-0.039 66.8

2.31 62.1

5.96 59.3

11.9 17 22.4 24.8 57.8 62.9 66.3 64.4 Saturation pressure [Pa]

24.4 67

20.3 69.5

13.4 8.23 2.97 68.6 65.2 65.2 Temperature [°C]

Equivalent air width of the 17 section: gc [g/m²] -16 -74 Ma [g/m²] 17 1 During Summer, the accumulated moisture Ma: accumulated moisture contents Gc: rate of condensation

dOUBLE sTUd assembly

May

20 53.2

6.8 [m]

For special materials you have to check condensed water: - porous materials800 g/m² 

Water presure [Pa]

Saturation pressure [Pa]

4.2 [m]

During Summer, the accumulated moisture dries out (March)

-

-

5.286

dries out (March)

The quantity of water condensed in the period -Graphs isn't bigger than 3% from the massJanuary of the wood in equivalent air thickness: - does not exceed 1% of the volume of insulation materials.

Equivalent air width of the section:

Security factor

Temperature [°C]

page 22

STUDY OF FIVE SECTIONS thermal performance An overview of the thermal performance for each wall assembly can be found in Table 4 below..

WALL ASSEMBLY

INSULATION PRODUCTS

TOTAL R-VALUE

Metal Stud

Spray Foam (5 1/2”) Polyiso (1”)

46

Wood Stud

Fiberglass (5 1/2”) Mineral Wool (5”)

43

CMU

Mineral Wool (4”) CMU

19

Double Wood Stud

Fiberglass (10 1/2”)

42

TJI

Cellulose (12”)

44

Table 4: R-Value Total for Each Wall Assembly

page 23

STUDY OF FIVE SECTIONS MATERIAL COST A General Contractor (GC), CVMNEXT Construction worked with us to estimate the cost of each wall assembly and associated products. Prices pertain to January 2015 in the North East region of the US. CVMNEXT, was also able to estimate the price difference between small (10k sf) and large (50k sf) scale building projects.

An estimated cost breakdown for each of the wall assemblies can be found in Table 5. The 10k sf open-shop cost of each assembly was used as an input in the Design Decision Matrix in section 3.2.

WALL ASSEMBLY

OPEN-SHOP 10K SF

OPEN-SHOP 50K SF

Metal Stud

$12,096

$11,773

Wood Stud

$11,447

$11,103

CMU

$14,256

$13,828

Double Wood Stud

$10,150

$9,846

TJI

$9,939

$9,641

Table 5: Cost Analysis of Five Wall Sections

page 24

STUDY OF FIVE SECTIONS END-OF-LIFE An overview of the end of life of the components in each assembly can be found in Table 6.

The last metric used in this research was an assessment of the wall assembly’s end-of-life (EOL). The goal of the EOL is to determine the recyclability and reusability of the products utilized in the assembly. For example, when a building is deconstructed, it is typical that the fiberglass insulation is disposed in a landfill, where as mineral wool can be salvageable for other uses, and gypsum board is sent to a recycling facility.

Each of the wall material EOL scenarios was determined by industry practices or information provided by product manufacturers. For products that were commonly sent to either a landfill or recycling facility, a weight was given to both categories when calculating the percentage of landfill versus recycle/salvage. An overview of each material’s EOL can be found in Table 6.

INSULATION

Wall Assembly

Wall Material

END-OF-LIFE SCENARIOS

Cedar Wood Tongue and Groove Siding

Recycle / Landfill

Cement Fiber Board Panel

Salvage / Landfill

Stone Veneer

Recycle / Salvage

WD Furring Strips

Recycle / Salvage

Air and Vapor Barrier

Recycle

Fiberglass Mat Gypsum Sheathing

Salvage / Landfill

Plywood Sheathing

Recycle

Oriented Strand Board

Recycle / Salvage

Metal Z Girts

Recycle

Steel/Metal Stud

Recycle / Salvage

Wood Stud

Recycle / Salvage

CMU Block

Recycle / Salvage

Masonry Anchor Ties

Recycle

Deep TJI

Recycle / Salvage

GWB

Recycle

Interior Paint

Recycle / Landfill

XPS

Salvage / Landfill

Fiberglass

Landfill

Mineral wool

Salvage / Landfill

Spray Foam

Landfill

Cellulose

Landfill

Table 6: End of Life Assessment

page 25

page 26

Metal Stud

STUDY OF FIVE SECTIONS END-OF-LIFE

METAL sTUD assembly

wOOD sTUD assembly

cmu assembly Wood Stud

Metal Stud

16%

14%

17%

27% 33%

42% 59% 42%

50%

Figure 4: Materials End-of-Life

Wood Stud

CMU

Double Wood Stud page 27

CMU

dOUBLE wOOD stud assembly

tji assembly Double Wood Stud TJI

6% 12%

44% 50%

44% 44%

TJI

Landfill Recycle Salvage

page 28

DESIGN DECISION ANALYSIS Based upon the five metrics analyzed in this research we have developed a Design Decision Matrix to more holistically evaluate various wall assemblies. The method for developing this Design Decision Matrix follows:

10-points were assigned to each metric in the Design Decision Matrix for a maximum total of 50 points per assembly.

The criteria points were determined by identifying the maximum and minimum of each of the metrics found in the study, and are reflected in Table 7.

qual weights were assumed across all five E metrics in this report. However, the Design Decision Matrix was developed such that the weighting of each metric could be adjusted to represent the needs and goals of the project. For example, you could weight the matrix so that cost, toxicity, and performance were twice as important as end of life and embodied carbon.

page 29

Cost

EFC kg Co2 eq.

Toxicity Red List Items

Thermal Performance R Value

End-of-Life

1

> $15,000

> 4,501

90% Yes or Exception + 10% No

< 20.5

100% Landfill

2

$14,001 to $15,000

4,001 to 4,500

80% Yes or Exception + 20% No

20.6–22

90% Landfill + 10% Recycle or Reuse

3

$13,001 to $14,000

3,501 to 4,000

70% Yes or Exception + 30% No

22.1–24

80% Landfill + 20% Recycle or Reuse

4

$12,001 to $13,000

3,001 to 3,500

60% Yes or Exception + 40% No

24.1–26

70% Landfill + 30% Recycle or Reuse

5

$11,001 to 12,000

2,501 to 3,000

50% Yes or Exception + 50% No

26.1–28

60% Landfill + 40% Recycle or Reuse

6

$10,001 to $11,000

2,001 to 2,500

40% Yes or Exception + 60% No

28.1–30

50% Landfill + 50% Recycle or Reuse

7

$9,001 to $10,000

1,501 to 2,000

30% Yes or Exception + 70% No

30.1–32

40% Landfill + 60% Recycle or Reuse

8

$8,001 to $9,000

1,001 to 1,500

20% Yes or Exception + 80% No

32.1–34

30% Landfill + 70% Recycle or Reuse

9

$7,001 to $8,000

501 to 1,000

10% Yes or Exception + 90% No

34.1–36

20% Landfill + 80% Recycle or Reuse

10

< $7,000

< 500

100% No

> 36

10% Landfill + 90% Recycle or Reuse

Criteria Points

Poor

Fair

Good

Better

Best

Table 7: Design Decision Matrix; ECF is calculated for all products in the wall assembly over the function unit (288 SF).

page 30

DESIGN DECISION ANALYSIS Evaluation of STUDY OF FIVE SECTIONS Overviews of the Design Decision scores are shown in Figure 5. The Design Decision scores reflect an equal weighting across the five metrics. While four out of five of the walls scored high in thermal performance, the double wood stud and the TJI walls were the overall best performers due primarily to their low embodied carbon footprint and low toxicity in their components.

Based on the Design Decision Matrix with all of the categories equally weighted, the ranking in descending order are:

1.

2.

3.

4.

5.

TJI Double Wood Stud Wood Stud Metal Stud CMU

page 31

Good

6

7 Better

8

9 Best

10

37

Cost Embodied Carbon Footprint Toxicity: Red List Thermal Performance: R-Value End-of-Life Cost

5

36

Embodied Carbon Footprint Toxicity: Red List Thermal Performance: R-Value End-of-Life Cost

4

21

Embodied Carbon Footprint Toxicity: Red List Thermal Performance: R-Value End-of-Life

Figure 5: Design Decision Scores for the Study of Five Sections

Cost

Fair

34

Embodied Carbon Footprint Toxicity: Red List Thermal Performance: R-Value End-of-Life Cost Embodied Carbon Footprint

2

28 Design Decision Score:

Toxicity: Red List

3

Thermal Performance: R-Value

Poor

End-of-Life 1

TJI Double Wood Stud CMU Wood Stud Metal Stud

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DESIGN DECISION ANALYSIS STUDY OF FIVE SECTIONS conclusion This type of holistic research can help design professionals tie together multiple sustainability metrics. It also illuminates the effects of material choices on the traditional metrics like cost and performance but, also the emerging priorities of environmental impact and health.

Process While this study presents results and analysis, it is fundamentally an investigation into the use of tools and a proposed methodology for helping us make better choices about our materials. At the conclusion of this part of the study, we started to ask ourselves how this type of work could be overlaid on the design process. Below is a proposed timeline for this research within the typical design process: Schematic Design 0% - Select criteria for evaluating design decisions.

Schematic Design 50% - Conceptualize potential wall assemblies Schematic Design 100% - Use Athena to perform a LCA - Evaluate the results; identify ECF hot spots and alter as necessary.

- Perform moisture diffusion modeling; alter as necessary to meet desired performance.

Design Development 50% - Select basis of design products for the assemblies - Conduct end of life research for those products - Begin Red List Research into those products - If an energy model is being used, compare energy usage to the assemblies Design Development 75% - Perform a wall section cost estimate using basis of design products and total project size to reflect any economy of scale in the estimate - Evaluate the costs; eliminate any out of the budget - Aggregate ECF, End of Life, Toxicity, and Cost information into the Design Decision Matrix and select the final assembly

Further Research The study did not directly address the idea of durability or longevity of the assemblies which is an equally important metric when selecting and proposing walls and roofs. Further research into this area is necessary to balance end of life consideration of products and materials.

Barriers to Materials Research

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There are a number of barriers we found in doing this type of work. Below we have listed some of the most common along with some simple suggestions to help you overcome them.

BARRIERS

SUGGESTIONS

Time & Cost: The additional metrics require more research and can compete with other resources needed for project design, construction, and coordination. While important this kind of research is rarely funded by clients.

- Start small. Give yourself an hour to dive as deep as you can into just one metric. Don’t worry if you don’t come to a conclusion; just make yourself smarter for the next time.

Utilizing Tools: Knowing where to find the best resources can become a challenge. Once you have the data, it can be equally difficult to crunch it.

Manufacturer Communication: Asking large companies for their ingredient lists or other detailed product information is no easy task.

Constant Change: Products and their components are continually changing which makes it difficult to stay current or build a resource library.

- Spread it out. Don’t spend all of your research time on one project. Look for opportunities to look at different metrics on different projects where they will have the most impact.

- Use lunch and learns to your advantage. Suggest and target manufactures for presentations that address material environmental and health impacts.

- Use your professional memberships. USGBC, Building Green, etc. have multiple webinars on metrics noted in the study. Catch a webinar while you’re eating lunch.

- Take short cuts. Use credible 3rd party certifications to identify environmentally responsible products.

- Read user manuals and watch how to videos. When the opportunity comes to do some of this work, you’ll already be past the learning curve.

- Establish Relationships. For frequently use manufactures, try to reach the same person with your questions and create rapport with them. Ask them to teach you about the ingredients in their product and their function. Help them understand why its important to you.

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NORMALIZED SECTION STUDY

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NORMALIZED SECTION STUDY Assembly Inventory The second part of the study aimed to compare assembly iterations within three assembly types: wood, metal, and CMU. Each of the wall assembly scenarios includes continuous insulation with a targeted R-value to align with the thermal performance requirements of the International Energy Conservation Code 2013. In each case, this R-value was achieved in a different way and the overall assembly was evaluated for: • • • •

Embodied Carbon Footprint Material Toxicity and Transparency Material Cost End-of-life

Each scenario was based upon the base cases noted in Table 8, with insulation types and thickness as the variable noted in Table 9.

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WOOD STUD ASSEMBLY

METAL STUD ASSEMBLY

CMU ASSEMBLY

Metal Cladding Exterior Insulation Air and Vapor Barrier Plywood Sheathing Cavity Insulation Wood Stud GWB Interior Paint

Metal Cladding Exterior Insulation Air and Vapor Barrier Plywood Sheathing Cavity Insulation Steel Stud GWB Interior Paint

Metal Cladding Exterior Insulation Metal Z Girts Air and Vapor Barrier CMU Block GWB Interior Paint

METAL STUD CASES

CMU CASES

Table 8: Normalized Wall Assembly Breakdown

WOOD STUD CASES Case 1: 1” XPS + 3 1/2” FG R-5 + R-15 =R-20

Case 1: 2” XPS + 3 1/2” FG R-10 + R-13= R-23

Case 2: 1 1/2” MW + 3 1/2” FG R-6.3 + R-15= R-21

Case 2: 2” MW + 3 1/2” FG R-8.4 + R-13= R-21

Case 3: 1” XPS + 2” SF R-5 + R-15 = R-20

Case 3: 2” XPS + 2” SF R-10 + R-14.8= R-25

Case 4: 1 1/2” MW + 2” SF R-6.3 + R-14.8= R-21

Case 4: 2” MW + 2” SF R-8.4 + R-14.8= R-23

Case 5: 1” XPS + 3 1/2” Cell R-5 + R-13= R-18

Case 5: 2” XPS + 3 1/2” Cell R-10 + R-13= R-23

Case 6: 1 1/2” MW + 3 1/2” Cell R-6.3 + R-13= R-19

Case 6: 2” MW + 3 1/2” Cell R-8.4 + R-13= R-21

Table 9: Insulation Combinations Tested for Each Wall Assembly

XPS: Extruded Polystyrene

Case 1: 2” XPS R-10 Case 2: 2 1/2” MW R-10.5

MW: Mineral Wool FG: Fiberglass SF: Spray Foam

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NORMALIZED SECTION STUDY Embodied Carbon footprint Athena Impact Estimator for Buildings Inputs in Normalized study

Three wall types were studied: metal stud, wood stud, and CMU.An overview of the life cycle inputs from Athena can be found in Table 10.

- - - -

The wall section has an area of 12’ x 24’ (functional unit) 50 year time span Average USA data Cradle to gate analysis

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INSULATION

Wall Assembly

Wall Material

Athena Input

Metal Cladding 26 GA

Metal Wall cladding 26 GA

Air and Vapor Barrier

Air Barrier

Metal Z Girts

Bolts Fastners clips

Plywood Sheathing

Softwood Plywood

Steel Stud

Galvanized Studs

Wood Stud

Small Dimension Softwood Lumber, kiln-dried

CMU Block

8" concrete block

GWB

5/8" Regular Gypsum Board

Interior Paint

Solvent Based Alked paint

XPS

Extruded Polystyrene

Fiberglass

FG Batt R 11-15

Mineral wool

MW Batt R 11-15

Spray Foam

Hand calculation

Cellulose

Blown Cellulose

Table 10: Athena Life Cycle Unit Processes

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NORMALIZED SECTION STUDY Embodied Carbon footprint Life Cycle Impact Assessment: Embodied Carbon Footprint (ECF) The weight and embodied carbon for the materials used in each of the normalized wall sections can be found in Figure 6.

- The material weight is consistent for each of the six insulation cases within the three wall assembly scenarios, averaging 2.0 (Wood Stud), 1.2 (Metal Stud), and 7.9 (CMU) short tons respectively (shown in Figure 6). The embodied carbon footprint impact ranges depending on the insulation combinations within each of the wall assembly scenarios. Out of the five insulation types analyzed, spray foam has the highest embodied carbon footprint across each wall assembly scenario.

- Wood Stud Assembly Base ECF: 1,458 kg of CO2 eq - Case 1, 2, 4 and 6, averaged 2,291 kg of CO2 eq.

- Case 3 and 4 averaged 3,692 kg of CO2 eq. or 38% higher than the other insulation cases.

- Metal Stud Assembly Base ECF: 1,520 kg of CO2 eq - Cases 1, 2, 5, and 6 averaged 2,320 kg of CO2 eq.

- Cases 3 and 4 averaged 3,721 kg of CO2 eq. or 40% higher.

- CMU Assembly Base ECF: 2,451 kg of CO2 eq - Cases 1, 2, 5, and 6 averaged 3,341 kg of CO2 eq.

- Cases 3 and 4 averaged 4,743 kg of CO2 eq. or 30% higher.

- With regard to the five different insulation products used in this study, spray foam has a significantly larger ECF than the other four. The XPS and mineral wool insulation used in this study are comparable to each other, followed by fiberglass insulation and cellulose. Cellulose had the lowest ECF, averaging 19 kg of CO2 eq. in each of the wall assembly cases.

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wood stud

Metal stud

CMu 4000

9

Cellulose

8

3500 Spray Foam

Embodied carbon

5

4

2500

2000

1500 3

2

weight

weight (metric tons) Weight of Wall Section (tonnes)

6

1000

500

13

14

15

16

17

18

19

20

21

22

23

24

25

26

Figure 6: Material Breakdown of Wall Assembly Scenarios. Left - Weight in Tonnes; Right- Embodied Carbon Footprint in kg CO2 eq.; XPS = Extruded Polystyrene, FG = Fiber Glass, SF = Spray Foam, MW = Mineral Wool, Cell = Cellulose

27

28

Case 2 MW

12

Case 1 XPS

11

0

Case 6 MW + Cell

10

Case 5 XPS + Cell

9

Case 4 MW + SF

8

Case 3 XPS + SF

7

Case 2 MW + FG

6

Case 1 XPS + FG

5

Case 4 MW + SF

4

Case 3 XPS + SF

3

Case 2 MW + FG

2

Case 1 XPS + FG

1

Case 6 MW + Cell

0

Case 5 XPS + Cell

1

Fiberglass

Embodied Carbon Footprint (kg of CO2 eq.)

3000

embodied carbon (kg CO2 eq.)

7

wood stud

Mineral Wool XPS Interior Paint GWB CMU Block Metal Stud Wood Stud Plywood Sheathing Air & Vapor Barrier Metal Z Girts Metal Cladding

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NORMALIZED SECTION STUDY MATERIAL TOXICITY + TRANSPARENCY Environmental Product Declarations (EPDs), Health Product Declarations (HPDs), Material Safety Data Sheets (MSDS), and other published product information were used to evaluate productâ&#x20AC;&#x2122;s toxicity and transparency. A summary of these findings per product can be found in Table 11.

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aSSEMBLY cOMPONENT LIST

Living Building Challenge v3 Red List

Environmental Product Declaration

Metal Cladding 26 GA: Englert

Red List Free - Unintentional Trace Amounts: Recycled Materials

Air and Vapor Barrier: Vaproshield: Wrap Shield

I10-E4 (9/2012): Proprietary Ingredients

Plywood: Roy O’Martin

Exception I10-E11 (1/2009): Composite Wood Sheet Goods

Metal Studs: Clark Dietrich

Red List Free Fully Disclosed

Wood Studs: Roy O’Martin

Red List Free Fully Disclosed

CMU Block: Fizzano Brothers Concrete Products

Red List Free Fully Disclosed

Gypsum Wall Board: USG Fiberrock Abuse Resistant Panels

Red List Free Fully Disclosed

Interior Paint: Sherwin Williams: Harmony

I10-E4 (9/2012): Proprietary Ingredients

Polyiso Insulation: DOW: Thermax CI

Exception I10-E21 (9/2010): HFRs in Foam Insulation exterior insulation

Industry Wide

Fiberglass Insulation: Knauf EcoBatt

DECLARE LABEL: Red List Free; Fully Disclosed

Product Specific

Mineral Wool Insulation: Thermafiber Rainscreen HD

Exception I10-E9 (3/2013): Phenol Formaldehyde in Mineral Wool Note - Outside of air barrier

Product Specific

Spray Foam Insulation: Demilec: Heat Lok Soy 200 Plus

Noncompliant: Foam insulation is not allowed in cavity-fill application as many Red List Free alternatives exist

Industry Wide

Cellulose Insulation: GreenFiber Cellulose

DECLARE LABEL: Red List Free; Fully Disclosed

Industry Wide

Table 11: Transparency Documentation for Normalized Wall Assemblies Components

Industry Wide

Industry Wide

Industry Wide

NORMALIZED SECTION STUDY thermal performance

METAL STUD

WOOD Stud

WALL ASSEMBLY

CMU

page 44

INSULATION COMBINATION

EXTERIOR R VALUE

INTERIOR R VALUE

TOTAL R VALUE

1

5

15

20

2

6.3

15

21.3

3

5

14.8

19.8

4

6.3

14.8

21.1

5

5

13

18

6

6.3

13

19.3

1

10

13

23

2

8.4

13

21.4

3

10

14.8

24.8

4

8.4

14.8

23.2

5

10

13

23

6

8.4

13

21.4

1

10

2

12

2

10.5

2

12.5

Table 12: R-Value Total for each of the Insulation Combinations

Each of the wall assembly scenarios targeted the thermal performance requirements of International Energy Conservation Code 2013. An overview of the thermal performance for each of the insulation combinations for the wall assembly cases, as described in Table 8, can be found in Table 12.

NORMALIZED WALL SECTION STUDY MATERIAL COST A General Contractor (GC), CVMNEXT Construction worked with us to estimate the cost of each wall assembly and associated products. Prices pertain to January 2015 in the North East region of the US. CVMNEXT, was also able to estimate the price difference between small (10k sf) and large (50k sf) scale building projects.

An estimated cost breakdown for each of the wall assemblies can be found in Figure 7. The 10k sf open-shop cost of each assembly was used as an input in the Design Decision Matrix in section 3.2.

14000 Interior Paint GWB

12000

CMU Block Steel Stud (2x4)

10000

Cost ( $ )

Wood Stud (2x4) Cellulose

8000

Spray Foam Fiberglass Insulation

6000

Plywood Sheathing Air and Vapor Barrier

4000

Mineral Wool (2.5") Mineral Wool (1.5")

2000

XPS (2") XPS (1")

0 1

2

3

4

5

6

1

Metal Stud Figure 7: Cost Analysis of Normalized Wall Section Study

2

3

4

Wood Stud

5

6

1

2

CMU

Metal Cladding

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NORMALIZED SECTION STUDY END-OF-LIFE (EOL) Each of the wall material EOL scenarios was determined by industry practices or information provided by product manufacturers. For products that were commonly sent to either a landfill or recycling facility, a weight was given to both categories when calculating the percentage of landfill versus recycle/salvage. An overview of each materialâ&#x20AC;&#x2122;s EOL can be found in Table 13.

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INSULATION

Wall Assembly

Wall Material

END-OF-LIFE SCENARIOS

Metal Cladding 26 GA

Recycle

Air and Vapor Barrier

Landfill

Metal Z Girts

Recycle / Salvage

Plywood Sheathing

Recycle

Steel Stud

Recycle / Salvage

Wood Stud

Recycle / Salvage

CMU Block

Recycle / Salvage

GWB

Recycle

Interior Paint

Recycle / Landfill

XPS

Salvage / Landfill

Fiberglass

Landfill

Mineral wool

Salvage / Landfill

Spray Foam

Landfill

Cellulose

Landfill

Table 13: Normalized Wall Study End-of-Life Scenarios

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DESIGN DECISION ANALYSIS A Design Decision Matrix was developed for the four metrics analyzed in the Normalized wall assembly study: cost, ECF, toxicity, and EOL (see Table 14). Thermal performance was not included in the Design Decision Matrix since each of the wall assemblies were designed to IECC 2013. The scoring method for the Design Decision Matrix is as follows:

10-points were assigned to each metric in the Design Matrix for a maximum total of 40 points per assembly.

The criteria points were determined by assessing the maximum and minimum of each of the metrics found in the study.

qual weights was assumed across all E four metrics in this report. However, the Design Decision Matrix was developed such that the user and/or client could adjust the weighting of each metric to represent the needs and goals of the project. For example, you could weigh the matrix so that cost, toxicity, and performance where twice as important as end of life and embodied carbon.

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Criteria Points

Cost

EFC kg Co2 eq.

Toxicity Red List Items

End-of-Life

1

> $15,000

> 4,501

90% Yes or Exception + 10% No

100% Landfill

2

$14,001 to $15,000

4,001 to 4,500

80% Yes or Exception + 20% No

90% Landfill + 10% Recycle or Reuse

3

$13,001 to $14,000

3,501 to 4,000

70% Yes or Exception + 30% No

80% Landfill + 20% Recycle or Reuse

4

$12,001 to $13,000

3,001 to 3,500

60% Yes or Exception + 40% No

70% Landfill + 30% Recycle or Reuse

5

$11,001 to 12,000

2,501 to 3,000

50% Yes or Exception + 50% No

60% Landfill + 40% Recycle or Reuse

6

$10,001 to $11,000

2,001 to 2,500

40% Yes or Exception + 60% No

50% Landfill + 50% Recycle or Reuse

7

$9,001 to $10,000

1,501 to 2,000

30% Yes or Exception + 70% No

40% Landfill + 60% Recycle or Reuse

8

$8,001 to $9,000

1,001 to 1,500

20% Yes or Exception + 80% No

30% Landfill + 70% Recycle or Reuse

9

$7,001 to $8,000

501 to 1,000

10% Yes or Exception + 90% No

20% Landfill + 80% Recycle or Reuse

10

< $7,000

< 500

100% No

10% Landfill + 90% Recycle or Reuse

Poor

Fair

Good

Better

Best

Table 14: Design Decision Matrix; ECF is calculated for all products in the wall assembly over the function unit (288 SF).

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DESIGN DECISION ANALYSIS Design Decision of NORMALIZED Wall Sections Findings: An overview of the Design Decision Matrix scores is shown in Figure 8. The Design Decision scores reflect an equal weighting across the four metrics. Below is the total embodied carbon footprint of each insulation combination.

WOOD STUD ASSEMBLIES

METAL STUD ASSEMBLIES

Case 1: 1” XPS + 3 1/2” FG (R-20) 169 kg of CO2 eq

Case 1: 2” XPS + 3 1/2” FG (R-23)

Case 2: 1 1/2” MW + 3 1/2” FG (R-21)

Case 2: 2” MW + 3 1/2” FG (R-21)

144 kg of CO2 eq Case 3: 1” XPS + 2” SF (R-20)

1,587 kg of CO2 eq Case 4: 1 1/2” MW + 2” SF (R-21)

1,562 kg of CO2 eq Case 5: 1” XPS + 3 1/2” Cell (R-18)

130 kg of CO2 eq Case 6: 1 1/2” MW + 3 1/2” Cell (R-19)

104 kg of CO2 eq

278 kg of CO2 eq 171 kg of CO2 eq Case 3: 2” XPS + 2” SF (R-25)

1,696 kg of CO2 eq Case 4: 2” MW + 2” SF (R-23)

1,589 kg of CO2 eq Case 5: 2” XPS + 3 1/2” Cell (R-23)

239 kg of CO2 eq Case 6: 2” MW + 3 1/2” Cell (R-21)

132 kg of CO2 eq

CMU ASSEMBLIES Case 1: 2” XPS (R-10)

220 kg of CO2 eq Case 2: 2 1/2” MW (R-10.5)

141 kg of CO2 eq

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30

26

25

20

20

25

23

25

25

6

6

19

19

23

24

22

21

25 6

6

6

20

6 6

15

5 6

6

6

6

5

6 5

6 5

10

6

6

7

7 4

7

7

6

4

6

6

Case 2

Case 3

5

6

5

6 EndͲofͲLife

6

Red List Items

4

6

6

Case 1

Case 2

5

6

5 7

5 7

6

6 5

5

7

6

7

5

5

4

4

5

5

5

Case 5

Case 6

Case 1

4

0 Case 1

Case 4

Case 5

Case 6

Wood Stud Figure 8: Design Decision Matrix Scores for Normalized Wall Study

Case 3

Case 4

Metal Stud

Case 2 CMU

ECF (kg CO2 eq.)

Cost ($)

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DESIGN DECISION ANALYSIS NORMALIZED Wall Section study conclusion In this portion of the study we chose to isolate insulation in this analysis as it is the component in a wall assembly that has the greatest effect on the projectâ&#x20AC;&#x2122;s operating energy. We wanted to determine how much it contributed to the other categories described in the study and thus, which insulation is the most environmentally preferred. In the proposed assemblies, the wood stud and metal stud walls composed of XPS and mineral wool on the exterior and fiberglass or cellulose insulation in the cavity scored the highest across all wall assemblies. Many of the insulation combinations, noted on the previous pages are within Athenaâ&#x20AC;&#x2122;s margin of error difference of 15%, making them essentially the same in terms of embodied carbon footprint.

Some final thoughts on insulation: Cellulose and fiberglass have low embodied carbon footprint and toxicity but, cellulose can be expensive and both fiberglass and cellulose must be disposed of in a landfill at this time.

Spray Foam, while it has a very high insulating value per inch, it performed poorly across the metrics evaluated.

XPS insulation performed poorly when it came to embodied carbon footprint and toxicity but, did well from a cost and end of life perspective.

Mineral wool was performed average in embodied carbon footprint, toxicity, and cost; and the best under end of life.

FINAL THOUGHTS & REFERENCES While “Thinking in Assemblies” presents research and findings, the realities of design, construction, and budget will often dictate the selection of some of the materials in any project. It is our hope that some of the ideas presented in this study have caught your interest and will one day help inform some of your work so that product selection in this new materials economy is not only defined by a limited number of factors but, a thoughtful investigation across multiple attributes that impact performance, the environment, and human health. We definitely learned from this study, and will carry our lessons learned into future work.

We welcome feedback and look forward to having a conversation with you.

ACKNOWLEDGEMENTS Thank you to Chris Boccella (CVMnext) for his support on material estimates, and Garrett McKissock (SIGA) for his support on moisture transport analysis using USai. References 1 - SPFA. Life Cycle Assessment of Spray Polyurethane Foam Insulation for Residential and Commercial Building Applications. Tech. Fairfax, VA: Spray Foam Polyurethane Foam Alliance, 2012. Print.

2 - “U.S. Life Cycle Inventory Database.” (2012). National Renewable Energy Laboratory, 2012. Accessed December 2012: https://www.lcacommons.gov/nrel/search 3 - Bushi, Lindita, Grant Finlayson, and Jamie Meil. A Cradleto-Gate Life Cycle Assessment of Ready Mixed Concrete Manufacture by NRMCA Members. Tech. N.p.: Athena Sustainable Materials Institute, 2014. Print.

4 - “Declare Products.” Product Database. International Living Future Institute, 2011. Web. 14 Dec. 2015.

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